Direct near-field mapping of nano-sphere-excited leaky surface modes atanisotropic metasurface

F Walla,R Malureanu,F Komissarenko,A Soltani,A Bogdanov,F Bürkle,I Sinev,A.V Lavrinenko,H G Roskos

doi:10.1088/1742-6596/1092/1/012165

Abstract

Leaky surface modes on an ultra-thin anisotropic gold metasurface are directly observed through scattering-type scanning near-field optical microscopy (s-SNOM). Surface modes are excited by focussing light onto a resonant silicon nano-sphere positioned on the surface by nano-manipulation under electron-beammonitoring. The light scattered from the nano-sphere is ableto excitesurface modes with a broad range of wavevectors. The asymmetric air-metasurface-insulator structure supports a leaky surface mode which is confined at the top interface and leaks into the higher-index substrate. s-SNOM near-field mapping of the leaky surface wave is in good agreement with the results of the full-wave simulationsof the electro-magnetic modes on the structure.

Highlights

Metasurfaces are two-dimensional periodic arrays of subwavelength elements[1]
Leaky surface modes on an ultra-thin anisotropic gold metasurface are directly observed through scattering-type scanning near-field optical microscopy
The light scattered from the nano-sphere is ableto excitesurface modes with a broad range of wavevectors.The asymmetric air-metasurface-insulator structure supports a leaky surface mode which is confined at the top interface and leaks into the higher-index substrate.s-SNOM near-field mapping of the leaky surface wave is in good agreement with the results of the full-wave simulationsof the electro-magnetic modes on the structure

Summary

Introduction

Metasurfaces are two-dimensional periodic arrays of subwavelength elements[1]. Due to strong interaction of the incident light and thesubwavelength scatterers forming the metasurface,abrupt changes of optical amplitude and phase can be introduced, which enablethe manipulation ofthe flow of light within ultra-smallvolumes. Leaky surface modes on an ultra-thin anisotropic gold metasurface are directly observed through scattering-type scanning near-field optical microscopy (sSNOM). Surface modes are excited by focussing light onto a resonant silicon nanosphere positioned on the surface by nano-manipulation under electron-beammonitoring.

Results

Conclusion